# Proving Congruent Triangles: Angle-Side-Angle and Angle-Angle-Side Theorem

In this lesson I will teach you the ASA (Angle-Side-Angle) and AAS (Angle-Angle-Side) theorems for proving triangles congruent.  The ASA theorem states that two triangles are congruent if there corresponding angle, side and angle measures are congruent.  Likewise, the AAS theorem states two triangles are congruent if they have a corresponding angle, angle and side measure.  Of course, the video will demonstrate the theorems more clearly so you need to watch the lesson to fully master the concepts.  Keep in mind that most of the theorems in this chapter have to do with “proving” two triangles congruent.  As such, the key skill you need to master about these theorems is writing proofs.  As I stated in previous lessons, you need to really work hard on proof writing- it’s not easy.  Math is about problem solving and critical thinking and writing proofs is an excellent way to develop these important aptitudes.  So after the lesson try to attempt as many proofs as possible- you will only get better as you do more problems.  Good luck!